Born in eastern Gaza City on February 1, 1958, Ramadan Abdullah Shallah studied at al-Zaqaziq University in Egypt, and heholds a Ph.D. in banking and economics from the University of Durham, England. From the late Seventies through the mid-Eighties, Shallah was an editorial board member for two periodicals that served as mouthpieces of the Islamic Jihad Movement in the Middle East: Al-Mukhtar Al-Islami (1979-81) and al Nour(1982-85); the latter was an Arabic monthly, published in Jerusalem.

Shallah was one of the early founders and leaders of the Gaza-based terrorist group Palestinian Islamic Jihad (PIJ), which was established in 1981 by Fathi Shikaki and others. Shallah held a seat on PIJ's Shura Council, essentially its board of directors. He also served a stint as head of the organization's London office; was responsible for transferring funds to finance PIJ activities in the West Bank and Gaza Strip; and wrote the text for many of the leaflets which the group distributed in those regions.

When Israeli authorities deported PIJ leader Fathi Shikaki to southern Lebanon in August 1988, Shallah played a major role in maintaining the integrity of the organization's infrastructure.

In 1990 and 1991, Shallah spoke at the annual conferences of the Islamic Committee for Palestine (ICP), which was, like its sister organization WISE, a PIJ front group founded by Sami Al-Arian. At the 1990 conference, Shallah delivered a speech calling for a relentless wave of Palestinian “martyrdom” operations against Israeli Jews. “There is currently a pervasive lie that there should be no armed Intifadah,” he said. “And we say that it is a lie because no one can claim that the armed struggle means arming the people in its entirety to face the occupation forces [using] weapons and fire instead of the stone. Demanding armed struggle means that the rifle which has been fighting throughout the years of jihad and struggle in Palestine must not cease and must not be silenced; rather, it [the rifle] must re-fire.”

In 1995 the FBI began to aggressively investigateWISE and ICP alike, on suspicion that they were affiliated with the Palestinian Islamic Jihad. That November, federal agents raided the offices of both Tampa organizations and seized all of their belongings. Sensing that the authorities were closing in on him, Shallah abruptly fled the United States and settled in Damascus, Syria.

When PIJ leader Fathi Shikaki was assassinated by Israeli Mossad agents on October 26, 1995, Shallah replaced him as the organization's secretary general. The following year, he addressed a group that included representatives of Hamas and Hezbollah, as well as a number of Iranians and several future suicide bombers. According to a federal U.S. indictment that was handed down in 2003, Shallah in that 1996 speech “mentioned past successful PIJ terrorist attacks” and vowed to “make the lives of the enemy’s leaders and their allies an explosion of hell and fire.”